I get brain fog while having penile erection in every early morning.

In the early morning when I am sleeping and having an penile erection, my brain get numb like something changing inside for 2 seconds then I immediately get exhausted and brain fog the whole day. Why does it happen?
I have quitted porn for almost 2 years and this symptom occurred 6 months ago, the same time after I tried antidepressants (Sertraline). I dont know if it relates to medicine. This really destroys my life because I have quitted permanantly.
If you have any idea please help me! Thank you very much!

 

Yes, It feels like I have to breath deeper to feel more comfortable. After that, I usually breath slower but deeper.